Re: [PATCH v4 2/5] x86/sgx: Reduce the locking range in sgx_sanitize_section()

Jarkko Sakkinen
2021-02-02T22:01:15Z

On Mon, Feb 01, 2021 at 09:26:50PM +0800, Tianjia Zhang wrote:
> The spin lock of sgx_epc_section only locks the page_list. The
> EREMOVE operation and init_laundry_list is not necessary in the
> protection range of the spin lock. This patch reduces the lock
> range of the spin lock in the function sgx_sanitize_section()
> and only protects the operation of the page_list.
>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>

I'm not confident that this change has any practical value.

/Jarkko

> ---
> arch/x86/kernel/cpu/sgx/main.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index c519fc5f6948..4465912174fd 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -41,20 +41,17 @@ static void sgx_sanitize_section(struct sgx_epc_section *section)
> if (kthread_should_stop())
> return;
>
> - /* needed for access to ->page_list: */
> - spin_lock(&section->lock);
> -
> page = list_first_entry(&section->init_laundry_list,
> struct sgx_epc_page, list);
>
> ret = __eremove(sgx_get_epc_virt_addr(page));
> - if (!ret)
> + if (!ret) {
> + spin_lock(&section->lock);
> list_move(&page->list, &section->page_list);
> - else
> + spin_unlock(&section->lock);
> + } else
> list_move_tail(&page->list, &dirty);
>
> - spin_unlock(&section->lock);
> -
> cond_resched();
> }
>
> --
> 2.19.1.3.ge56e4f7
>
>